The present invention relates to analytical instruments for detecting and identifying trace levels of selected vapors, and in particular to portable instruments. The present invention has particular application to rapid detection and identification of trace air contaminants such as cocaine or heroin.
It is known to preconcentrate analytes in air samples by the use of sorbents, and thereby increase the sensitivity of detecting instruments. The aforementioned copending U.S. application Ser. No. 330,654 discloses the use of an absorption preconcentrating air sampler to increase the sensitivity of an analytical instrument. In such a sampler, a substantial portion of the analyte contained in a large volume of air becomes absorbed in a small volume of liquid extractant that can be injected directly into an analytical instrument, such as a liquid chromatograph. As compared with other methods, the direct absorption of an analyte from an arbitrarily large volume of air into a small volume of liquid extractant offers the advantages of low-temperature operation, simplicity, speed and flexibility. That device has proved effective for detecting hazardous analytes, such as highly carcinogenic primarily aromatic amines, when used with gas or liquid chromatographs.
Liquid-absorption sampling has been used successfully for the collection of many different analytes, including trinitrotoluene, alkaloids, primary aromatic amines, hydrazines, hydrogen peroxide, nitrogen oxide, diisocyanates, 2-chloronitrobenzene, and several inorganic halogen compounds (HCl, HF, F.sub.2, and other hydrolyzable fluorides). Preferably, as disclosed in copending application Ser. No. 330,654, the extractant should react rapidly with the analyte to yield a light-absorbing or light-emitting product that can be measured colorimetrically or by chemiluminescence using a built-in, preferably fiber-optic, detector. This would yield a portable yet highly sensitive, near real-time, self-contained analytical instrument. Alternatively, near real-time recording of sampled air compositions can be obtained by feeding the collected liquid into separate properly marked vials at predetermined intervals.
It is also recognized that many chemical compounds tend to be preferentially adsorbed onto solid surfaces, especially air-borne solid particulates, or absorbed by liquids, especially water droplets. This is true of most explosives and at least some propellants and chemical warfare agents. Therefore, suspended liquid and solid particulates may serve as natural preconcentrators. It would be advantageous to collect analytes from air-borne water droplets and/or particulates. This advantage is not readily offered by alternative types of preconcentrators.
Copending U.S. application Ser. No. 330,655 provides for the applicability of the absorption preconcentrating sampler of the aforementioned copending U.S. application Ser. No. 330,654 by coupling it with other types of analytical techniques to effect detection of a wide variety of analytes. A further advanced high-throughput liquid-absorption preconcentrator (HTLAP) is herein disclosed which incorporates the preconcentrating sampler of copending U.S. application Ser. No. 330,655 and the analytical system of copending U.S. application Ser. No. 330,654, and which further provides for rapid detection and analysis of trace air contaminants.